Powders are solid dosage forms containing dry mixtures of finely divided medicinal and non-medicinal agents intended for internal or external use. It is a solid substance in finely divided state (varying 10nm-1000μm) and typically obtained by crushing, grinding, or comminuting.
Powder applications are expanding in a variety of highly developed fields, such as foods, cosmetics, chemicals, and many other fundamental fields, particularly in pharmaceuticals. The majority of active pharmaceutical ingredients (APIs) are administered as solid dosage forms, prepared by processing and formation of powders.
Although the use of powders as a dosage form has been replaced largely by the use of tablets and capsules in modern medicine, they represent one of the oldest dosage forms and present certain advantages that have led to their continued use as pharmaceutical dosage forms. This article focuses on these advantages as well as disadvantages of powder dosage forms.
Advantages of Powders
1. There is a wide choice of ingredients, and the dose can easily be achieved for patient administration.
2. Powders have better physicochemical stability and longer shelf life compared to liquid dosage forms. For example, the shelf life of powders for antibiotic syrups is 2 to 3 years, but once reconstituted with water it is 1 to 2 weeks.
3. Children and adults who have trouble swallowing tablets or capsules may find powders more acceptable.
4. A large dose that cannot be administered in other forms can be administered as powder. For example, if the dose of a drug is 1 to 5 g it is sometimes not feasible to manufacture tablets to supply the drug to the patient.
5. A rapid dispersion of drugs occurs in the stomach when given in powder forms rather than in compressed form.
6. Dissolution rate of oral powders containing water-soluble drugs is generally faster than tablets or capsules, in which disintegration of the tablet or the capsule shell is required prior to dissolution.
7. A powder can be dispersed in water or another liquid and more easily swallowed.
8. Oral powders can be mixed with beverage or applesauce immediately before use.
9. Manufacturing of powder dosage form is economic, hence, product cost is quite economic as compared to other dosage forms.
10. Powders offer a lot of flexibility in compounding solids.
Disadvantages of powders
1. Powders are not the dosage form of choice for drugs with unpleasant taste. This is because masking of unpleasant tastes may be a problem with this type of preparation.
2. Drugs that deteriorate rapidly with exposure to atmosphere or acidic pH should not be dispensed as powders. For example, ferrous iron salts are easily oxidized and should not be administered as powders.
3. Powders are bulky and inconvenient to carry.
4. Powders are not a suitable dosage form for the administration of drugs that are inactivated in the stomach or drugs which can cause damage to the stomach.
5. Dispensing potent drugs requiring low doses as powders (e.g., bulk powders) may not be appropriate. This is because individual doses are usually extracted from the bulk using a 5 ml spoon, which is subject to variation in spoon fill (e.g., level or heaped spoonfuls).
6. Powders are not well suited for dispensing hygroscopic or deliquescent drugs.
References
- Dash, A., Singh, S. and Tolman, J. (2014). Pharmaceutics – Basic Principles and Application to Pharmacy Practice. USA: Academic Press.
- Ghosh, T. and Jasti, B. (2005). Theory and Practice of Contemporary Pharmaceutics. USA: CRC Press LLC.
